Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case M I C R O B I O L O G Y a n i n t r o d u c t i o n ninth edition TORTORA  FUNKE  CASE 15 Microbial Mechanisms of Pathogenicity

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Mechanisms of Pathogenicity  Pathogenicity: The ability to cause disease.  Virulence: The extent of pathogenicity.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Portals of Entry  Mucous membranes  Skin  Parenteral route

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Numbers of Invading Microbes  Dosage Amounts  ID 50 : Infectious dose for 50% of the test population.  LD 50 : Lethal dose (of a toxin) for 50% of the test population.  Examples  Botulinum 0.03 ng/kg  Shiga toxin 250 ng/kg  Staphylococcal enterotoxin 1350 ng/kg

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Portal of EntryID 50 Skin10-50 endospores Inhalation10,000-20,000 endospores Ingestion250,000-1,000,000 endospores Bacillus Anthracis Infectious Dosage

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Adherence  Adhesions/ligands bind to receptors on host cells  Glycocalyx  Biofilms  Fimbriae  Pili  Flagella

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Enzymes  Bacterial Capsules  Help Prevent Phagocytosis  Increase Virulence  Anchor Bacterial Cells

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Penetration into the Host Cell Figure 15.2

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Toxins  Toxin: Substances that contribute to pathogenicity.  2 main types of toxins  Toxigenicity: Ability to produce a toxin.  Toxemia: Presence of toxin in the host's blood.  Toxoid: Inactivated toxin used in a vaccine.  Antitoxin: Antibodies against a specific toxin.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Source:Gram – Relation to microbe:Present in LPS of outer membrane Chemistry:Lipid Fever?Yes Neutralized by antitoxin?No LD 50 :Relatively large Figure 15.4b Endotoxins

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exotoxin Source:Mostly Gram + Relation to microbe:By-products of growing cell Chemistry:Protein Fever?No Neutralized by antitoxin?Yes LD 50 :Small Figure 15.4a Example: Botulinum Toxin

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exotoxins  A-B toxins Figure 15.5

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exotoxins  Membrane-disrupting toxins  Lyse host’s cells by  Making protein channels in the plasma membrane  Disrupting phospholipid bilayer.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exotoxins  Superantigens  Cause an intense immune response due to release of cytokines from host cells.  Fever, nausea, vomiting, diarrhea, shock, and death.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exotoxins  Specific for a structure or function in host cell Figure 15.4a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exotoxins Exotoxin Lysogenic conversion Corynebacterium diphtheriae A-B toxin. Inhibits protein synthesis. + Streptococcus pyogenes Membrane-disrupting. Erythrogenic. + Clostridium botulinumA-B toxin. Neurotoxin+ C. tetaniA-B toxin. Neurotoxin Vibrio choleraeA-B toxin. Enterotoxin+ Staphylococcus aureusSuperantigen.+

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Source:Gram – Relation to microbe:Present in LPS of outer membrane Chemistry:Lipid Fever?Yes Neutralized by antitoxin?No LD 50 :Relatively large Figure 15.4b Endotoxins

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Endotoxins Figure 15.6 The fever caused by endotoxin release:

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cytopathic Effects of Viruses Table 15.4

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Portals of Exit  Respiratory tract  Coughing and sneezing  Gastrointestinal tract  Feces and saliva  Genitourinary tract  Urine and vaginal secretions  Skin  Blood  Biting arthropods and needles or syringes

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of Pathogenicity Figure 15.9